The present invention concerns a trimming potentiometer in T- or Pi-network connection with three parallel resistance paths located in a plane on an insulating plate. Along these resistance paths, wiper contacts fastened to a common carrier and moving in the same direction can be displaced. The carrier is in operative connection, through lengthwise displacement, with a screw spindle.
Trimming potentiometers of this species are already known from the German patent Dt-GM 1,957,345 as adjustable attenuator pads. They contain wiper contacts which are located in a plane normal to the longitudinal direction of the resistance paths. These attenuator pads are in particular for common antenna installations, and serve for adjusting to a desired attenuation between two high-frequency connections.
In a trimming potentiometer design known from German patent DT-OS 1,926,199, the carrier for the wiper contacts is provided with a trough-shaped cross section and can be displaced by sliding action along the screw spindle.
German patent DT-PS 1,540,339 provides for the use of a sleeve for the wiper contacts. This sleeve is slipped over the screw spindle and has a reinforcing portion with a depth approximately equal to the depth of thread of the screw spindle, located at an angle equivalent to the pitch angle of the screw spindle.
Based on this state of the art, it is an object of the present invention to further improve a trimming potentiometer of the character described above.
Another object of the present invention is to provide a trimming potentiometer which is simple in design and may be easily fabricated.
Another object of the present invention is to provide a trimming potentiometer with substantially long operating life.